3.8亿岁罕见鱼类化石 幼仔与母亲脐带相连
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北京时间5月30日消息,据美国生活科学网报道,科学家最近发现了3.8亿年前一条即将生育幼仔的盾皮雌鱼化石,这是迄今发现的最古老胎生鱼化石。虽然这条雌鱼已经死亡,但是从化石标本上可清晰地看到一条即将出生的胚胎幼仔和母亲的脐带相连。
这项研究使远古鱼类胎生的历史向前追溯了2亿年,支持了脊椎动物体内受精起源于远古鱼类的观点。澳大利亚维多利亚博物馆古生物学家约翰·朗说,“当我第一次看到雌性鱼化石标本中包含着胚胎幼仔,我非常吃惊。通过研究最早期脊椎动物交配,我渐渐认识到,远古鱼类不仅会在水中排卵,还会在水中交配胎生幼仔。”
新发现的化石标本是一种叫做“Materpiscis
attenboroughi”的盾皮鱼,该物种现已灭绝,生活在4.17-3.54亿年前泥盆纪时期的海洋之中。这条远古雌性盾皮鱼长度不足10英寸(25厘米),其腹内的幼仔是成年鱼体大小的25%。昆士兰州立大学的史蒂文·索尔兹伯里说,“相对于母体来说,其胚胎幼仔的身体较大,这表明该鱼类幼体出生时就是成型的,这种生殖策略可以避免幼仔出生后被其他大型鱼类掠食。”
朗和研究小组成员还分析了之前发现的盾皮鱼标本,他们发现可能3个鱼类标本中可能包含着胚胎幼仔,它们与最新发现的这具标本生活于同一时期。
对比现代鳐和鲨鱼,即将生育的盾皮鱼显示许多原始鱼类已具有高级复杂的生殖生物系统,有关研究发表于5月29日出版的《自然》杂志上。
据悉,记录动物即将出生的化石标本非常罕见,2006年科学家曾宣称发现1亿年前即将生育的鱼龙化石标本。(魏 冬)
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